A new type of electric washing machine has been proposed. We name it a "drum type" of washing machine. It has a drum which rotates around a horizontal axis, unlike the conventional washing machine with a drum which rotates around a vertical axis. We now call the drum of the former a "vertical drum", because the rotation plane of the drum is a vertical plane. When we place the washing and cleaning material in the vertical drum, shut the cover and turn on the switch, all processes of laundering-washing, rinsing, dehydrating and also drying--are automatically done in succession by changing the rotation speed of the drum in two stages. In the washing and rinsing processes, the vertical drum rotates at a low speed with water, alternatively in both directions--clockwise and counterclockwise. In the dehydrating process, the vertical drum rotates at a high speed without water in one direction. In the drying process, the drum rotates at the low speed under application of heat without water in both directions or in one direction.
In comparison with the conventional electric washing machine, the drum-type washing machine is advantageous in that it can complete the laundering process, including drying, in the same drum and save water in the washing and rinsing processes.
The drum type of electric washing machine requires two different drum rotation speeds according to the various laundry processes. In addition, it is preferable that the drum can rotate both in a clockwise direction and in a counterclockwise direction. Thus, in the drum type of washing machine, the drum is required to rotate at two different speeds, both clockwise and counterclockwise.
For this purpose, an apparatus for changing the rotational speed of a mechanism which comprises a motor with a convertible number of poles (four poles in the washing process and two poles in the dehydrating process), a centrifugal clutch and a reduction gear was invented. Namely, this apparatus can select two states of transmission; one state is where the motor shaft is connected by a reduction gear to the output shaft and the other is where the motor is directly connected to the output shaft. Either of the two states is selected by two clutches.
However, this apparatus requires at least two clutches for converting speed. Further, the clutch which connects the carrier of the reduction gear with the output shaft has a very complicated structure. Further yet, in the case of high speed rotation, the drum can rotate in only one direction, because a centrifugal clutch which is inherently unilateral connects the motor shaft to the output shaft. Thus, the drum cannot rotate both clockwise and counterclockwise at high speed.
Japanese Patent Laying Open. No. 57-65424 (Apr. 21, 1982) has proposed an apparatus which can convert the rotation speed of a mechanism at two stages by changing the direction of rotation. This apparatus uses a ratchet which also has an inherently unilateral character. For example, the rotation torque can be transmitted only clockwise in the high speed state and counterclockwise in the low speed state. It can not be used as the driving device of the drum type of washing machine, because of its double-unilateral character.
Japanese Patent Laying Open No. 58-24643 (Feb. 14, 1983) has proposed another apparatus which can convert the rotation speed of a mechanism using a planetary gear unit. The internal gear is fixed to the casing. The carrier is not connected to the output shaft directly, but intermediately by a collar which can be moved in an axial direction on the surface of the output shaft. When the collar is moved toward the input shaft, the collar connects the output shaft with the input shaft and the output shaft rotates rapidly. When the collar is moved toward the output shaft, the collar connects the output shaft with the carrier of the planetary gear unit and the output shaft rotates slowly.
The purpose of this invention is to provide an apparatus for changing the rotational speed of a mechanism which can transmit rotational torque both clockwise and counterclockwise, at both a high speed level and at a low speed level.